NETGEAR D8500 User Manual page 251

2. Your IRC client composes a request message to an IRC server using a destination port number of 6667, the
standard port number for an IRC server process.Your computer then sends this request message to your
modem router.
3. Your modem router creates an entry in its internal session table describing this communication session between
your computer and the IRC server.Your modem router stores the original information, performs Network
Address Translation (NAT) on the source address and port, and sends this request message through the
Internet to the IRC server.
4. Noting your port triggering rule and observing the destination port number of 6667, your modem router creates
another session entry to send any incoming port 113 traffic to your computer.
5. The IRC server sends a return message to your modem router using the NAT-assigned source port (for
example, port 33333) as the destination port and also sends an "identify" message to your modem router with
destination port 113.
6. When your modem router receives the incoming message to destination port 33333, it checks its session table
to see if a session is active for port number 33333. Finding an active session, the modem router restores the
original address information replaced by NAT and sends this reply message to your computer.
7. When your modem router receives the incoming message to destination port 113, it checks its session table
and finds an active session for port 113 associated with your computer.The modem router replaces the
message's destination IP address with your computer's IP address and forwards the message to your computer.
8. When you finish your chat session, your modem router eventually senses a period of inactivity in the
communications.The modem router then removes the session information from its session table, and incoming
traffic is no longer accepted on port numbers 33333 or 113.
AC5300 WiFi VDSL/ADSL Modem Router Model D8500
Manage Port Forwarding and Port Triggering
251